Method and system for providing DC power on local telephone lines
View Patent ↗A telephone unit device connectable in series between a telephone set and a wire pair coupled to a telephone service and carrying DC power and an AC telephone signal. The device includes: a first connector connectable to the wire pair; a second connector connectable to the telephone set; means connected between the first and second connectors for passing substantially without change the AC telephone signal between the wire pair and the telephone set; and means connected between the first and second connectors for receiving DC power only from the wire pair and converting the DC power to a level suitable for proper telephone operation of the telephone set connected thereto.
1. A telephone unit device connectable in series between an analog telephone set and a wire pair coupled to a telephone service and carrying DC power and an analog telephone signal, said device comprising: a first connector connectable to the wire pair; a second connector connectable to the telephone set; a signal passing circuit connected between said first and second connectors for passing substantially without change the analog telephone signal between the wire pair and the analog telephone set; and a DC/DC converter connected in series between said first and second connectors for receiving DC power only from the wire pair and converting the DC power to a level suitable for proper telephone operation of the analog telephone set connected thereto
wherein:
said signal passing circuit comprises a transformer composed of a primary winding and a secondary winding and first and second capacitors, each said capacitor being connected in series with a respective one of said windings; and
said DC\DC converter is connected between said first and second capacitors.
2. The device of claim 1 integrated into one of: an analog telephone set; and a telephone outlet.
3. An outlet comprising the telephone unit device of claim 1 .
4. The device of claim 1 in combination with:
an off-hook detector couplable to the analog telephone set for detecting an off-hook condition of the analog telephone set;
an off-hook transmitter coupled to said off-hook detector and to the wire pair for supplying an off-hook indication to the wire pair in response to detection of an off-hook condition by said off-hook detector.
5. The device of claim 4 , wherein the off-hook indication is a signal composed of one or more tones.
6. The device of claim 4 , wherein said off-hook indication is provided by a variable impedance that assumes a selected value to produce the off-hook indication.
7. The device of claim 4 , wherein the off-hook indication is a message sent over a data communication network.
8. The device of claim 7 , wherein the data communication network uses the wire pair as a communication medium.
9. The device of claim 1 , wherein:
each of said primary and secondary windings has a center tap; and
each of said first and second capacitors is connected to the center tap of a respective one of said primary and secondary windings.
10. The device of claim 1 , wherein the telephone set is connectable to only said second connector.